The human eye is a complex optical system. Vision begins when light enters the eye through the cornea, the front clear “window” of the eye responsible for focusing light rays to the back of the eye. From there, it travels through clear aqueous fluid, and passes through a small aperture in the iris, the colored structure which rests behind the cornea and in front of the natural lens. The opening in the center of the iris is the pupil. The iris acts like a camera shutter and controls the amount of light that enters the eye. As muscles in the iris relax or constrict, the pupil changes size to adjust the amount of light entering the eye. Light rays are focused through the lens and proceed through a clear jelly-like substance in the center of the eye called vitreous, which gives it form and shape. When light rays finally land on the retina, the part of the eye similar to film in a camera, they form an upside-down image. The retina contains millions of photo-receptor cells which convert light into images. The retina converts the image into an electrical impulse that travels along the optic nerve to the brain, where it is interpreted as an upright image.
Usually resulting from unexplained birth defects, coloboma describes a situation where a portion of the structure of the eye is lacking. This gap can occur in a range of areas and can be large or small. It can appear as a black notch of varying depth at the edge of the pupil, giving the pupil an irregular shape. The most common form of gap is caused by an imperfect closure of a cleft, present in the womb but usually closed by birth date. This gap can occur in the eyelid, iris, lens, choroid or optic disc. This does not mean that there is a hole in the eye, just that certain structures within the eye do not fully form. Coloboma of the iris may sometimes give the appearance of a keyhole in the pupil.
Attempts have been made to address the problems affecting patients suffering from coloboma of the iris by providing iris reconstruction implants. However, the implants of the prior art have been complicated multiple-piece lens which are cumbersome and uncomfortable. The methods of implantation have required complicated implantation techniques. Certain of these implants and methods are discussed next.
U.S. Pat. No. 6,280,469 to Terry et al describes an implantable artificial iris device in the form of a thin, generally annular wafer or web that is colored to replicate the appearance of an iris. The device is implanted either within the region known as the ciliary sulcus or in the region of meeting or joinder of the anterior and posterior capsules and within the realm of the capsular bag. In either case, the method of implantation involves surgical trimming of the natural iris. Implantation is by way of “a circular threading (or snaking)” of the implants into the eye chambers.
U.S. Pat. No. 5,628,797 to Richer describes a cosmetic anterior chamber intraocular lens and implantation method, wherein the lens is a multiple-piece lens with a circular joint or hinge and locking latch. The patent describes the implantation of the lens with haptics, or lens support elements, which are provided for keeping the lens in position in “angle structures of the eye”. The haptics, which are depicted schematically in the patent, must be “opened” after insertion into the anterior chamber to perform their function.
Although the haptics (or lens support elements) for use with the Richer implants are described only schematically in the patent, the prior art is replete with descriptions of haptics that may be used with ocular implants. By way of example, U.S. Pat. No. 6,224,628 to Callahan et al describes in the Background portion thereof a number of patents that have issued for these lens supporting elements. These patents, and the Callahan et al patent itself, describe haptics of a variety of shapes and geometries, all of which have drawbacks relating to their insertion, manufacture and/or use. In particular, the prior art haptics make the prior art implants employing the same more difficult to insert into the eye and, at least in certain instances, undesirable in use. What has been needed is an implant that can be used, for example, by patients suffering from coloboma of the iris and that is implantable in the eye of a patient in a simple and straightforward manner without the use of the complicated haptics of the prior art.